IVGCVSW-7663 Updated BuildGuideAndroidNDK script in Arm NN

* Download CMake 3.19 before building Flatbuffers

Signed-off-by: John Mcloughlin <john.mcloughlin@arm.com>
Change-Id: Ib7e897e3d4a5636e5e14a7bf3c593efa7982c4e2
diff --git a/scripts/build_android_ndk_guide.sh b/scripts/build_android_ndk_guide.sh
index e667c7f..90a2e33 100755
--- a/scripts/build_android_ndk_guide.sh
+++ b/scripts/build_android_ndk_guide.sh
@@ -422,13 +422,13 @@
     echo "Downloading Android NDK failed"
     exit 1
 fi
+GetAndBuildCmake319
+CMAKE=$WORKING_DIR/cmake/install/bin/cmake
 GetAndBuildFlatbuffers
 if [[ $? != 0 ]] ; then
     echo "Building Flatbuffers failed"
     exit 1
 fi
-GetAndBuildCmake319
-CMAKE=$WORKING_DIR/cmake/install/bin/cmake
 GetArmNN
 if [[ $? != 0 ]] ; then
     echo "Cloning Arm NN failed"